Large 28.2 MB PDF schematic for the Samsung Galaxy S4, model GT-I9505. The size suggests a fairly complete service document, likely including detailed circuit pages and possibly board layout views, though contents should be checked. It is used for tracing power rails from the PMIC, charging, baseband and RF lines, and for finding test points and component positions during micro-soldering repairs. Any PDF viewer will open it. Several S4 variants exist with different hardware, so confirm the GT-I9505 code on the device before following it.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @Schematics_Mobile. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.